Projective Geometry

La géométrie est une espèce de hochet que la nature nous a jeté pour nous consoler et nous amuser dans les ténèbres.

(Jean-Baptiste le Rond d'Alembert to Friedrich II.)

This program started as a small JavaScript exercise — just a little more than the infamous “Hello world”... It visualizes the real projective plane. It provides elementary constructions of points, lines and conic sections. You can also try out the examples of predefined sequences of constructions.

Some elements (e.g. circles, reflections, midpoints) depend on the geometry, that is the measurement of distances and angles, defined via double ratios with respect to the absolute conic (the horizon). Any type of Cayley-Klein geometry can be chosen.

left-button drag	shift the drawing plane
middle-button drag	rotate the drawing plane
right-button drag	tilt the drawing plane
mouse wheel	scale the drawing plane
double-touch drag	shift/rotate/scale the drawing plane
triple-touch drag	tilt the drawing plane